Effects of 120 vs. 60 and 90 g/h Carbohydrate Intake during a Trail Marathon on Neuromuscular Function and High Intensity Run Capacity Recovery

ground: Current carbohydrate (CHO) intake recommendations for ultra-trail activities lasting more than 2.5 h is 90 g/h. However, the bene ts of ingesting 120 g/h during a mountain marathon in terms of post-exercise muscle damage have been recently demonstrated. Therefore, the aim of this study was to analyze and compare the e ects of 120 g/h CHO intake with the recommendations (90 g/h) and the usual intake for ultra-endurance athletes (60 g/h) during a mountain marathon on internal exercise load, and post-exercise neuromuscular function and recovery of high intensity run capacity. Methods: Twenty-six elite trail-runners were randomly distributed into three groups: LOW (60 g/h), MED (90 g/h) and HIGH (120 g/h), according to CHO intake during a 4000-m cumulative slope mountain marathon. Runners were measured using the Abalakov Jump test, a maximum a half-squat test and an aerobic power-capacity test at baseline (T1) and 24 h after completing the race (T2). Results: Changes in Abalakov jump time (ABKJT), Abalakov jump height (ABKH), half-squat test 1 repetition maximum (HST1RM) between T1 and T2 showed signi cant di erences

4000-m cumulative slope mountain marathon. Runners were measured using the Abalakov Jump test, a maximum a half-squat test and an aerobic power-capacity test at baseline (T1) and 24 h after completing the race (T2). Results: Changes in Abalakov jump time (ABKJT), Abalakov jump height (ABKH), half-squat test 1 repetition maximum (HST1RM) between T1 and T2 showed signi cant di erences by Wilcoxon signed rank test only in LOW and MED (p<0.05), but not in the HIGH group (p>0.05). Internal load was signi cantly lower in the HIGH group (p=0.017) regarding LOW and MED by Mann Whitneyutest. A signi cantly lower change during the study in ABKJT(p=0.038), ABKH(p=0.038) HST1RM(p=0.041) and in terms of fatigue (p=0.018) and lactate (p=0.012) within the aerobic power-capacity test was presented in HIGH relative to LOW and MED. Conclusions: 120 g/h CHO intake during a mountain marathon might limit neuromuscular fatigue and improve recovery of high intensity run capacity 24 h after a physiologically challenging event when compared to 90 g/h and 60 g/h. Keywords: resistance; carbohydrates; fatigue; recovery; gut training; performance; gastrointestinal discomfort; absorption Nutrients2020,12, 2094; doi:10.3390 /nu12072094 /journal/nutrients

Nutrients2020,12, 2094 2 of 17 1. Introduction Participation in ultra-endurance mountain race events (>4 h) has increased in recent years [1]. The di erent distances run by participants range from mountain marathons (42,195 m) to multistage ultra-marathons (up to 350 km), with an accumulative altitude gain of 24,000 m during the most extreme events [2]. In addition, mountain athletes are exposed to di erent environmental conditions, such as irregular terrains with a variety of geographical and topographic characteristics, climatic conditions, altitude exposure and temperature uctuations [2–4]. This results in extreme physiological demands which may cause, among other things, negative energy balance, dehydration, decrease in blood glucose levels, muscle and hepatic glycogen depletion, exercise induced muscle damage (EIMD) and in ammation [2–5], and therefore might induce high levels of neuromuscular fatigue [2,6]. In this sense, the fatigue experienced by the runner could be quanti ed by monitoring the internal exercise load (determined by intensity (measured or perceived) time) endured by an athlete during exercise [7,8] and by looking for di erent strategies that allow it to be delayed [7]. Carbohydrate (CHO) intake during endurance exercise has been shown to delay neuromuscular fatigue and improve exercise capacity and work rate signi cantly in a dose–response relationship [9,10]. In this sense, although the current recommendations in events lasting more than 2.5 h include the 90 g/h CHO intake [11,12], a gut training avoids gastrointestinal discomfort that it could facilitate the intake of greater amounts of CHO to the recommendations [13]. In this sense, although>90 g/h CHO intake may have controversial results [9,14], Pfei er et al. showed that athletes who consumed 120 g/h were among the fastest during two ultraendurance events, indicating a delay in the onset of fatigue [10]. In addition a study carried out by our lab has recently demonstrated that higher CHO intake (120 g/h) than recommended could be a determining factor in the internal exercise load response and could limit exercise-induced muscle damage (EIMD) in elite trail runners 24 h after completing a mountain marathon, suggesting that recovery time after such an endurance event could be shortened by a

study carried out by our lab has recently demonstrated that higher CHO intake (120 g/h) than recommended could be a determining factor in the internal exercise load response and could limit exercise-induced muscle damage (EIMD) in elite trail runners 24 h after completing a mountain marathon, suggesting that recovery time after such an endurance event could be shortened by a suitable CHO intake during exercise [15]. In addition, it is well known that CHO substrate availability plays a central role in peripheral fatigue, but also within the central nervous system and, thus, in central fatigue [16]. Stewart et al. [17] showed that glucose intake (1.23 0.11 g/kg body mass) during exercise with a 15-min frequency in 15 untrained participants improved muscle function due to attenuated disturbances in the membrane excitability, suggesting that peripheral fatigue could be delayed by CHO intake during exercise. Peripheral fatigue is understood as the failure of local mechanisms in the muscle and, therefore, the decrease in the contraction and relaxation function that are related with the energetic status of the muscle cell [18,19]. Among these mechanisms, the potential action in the sarcolemma, the excitation–contraction (E-C) coupling and the interaction between actin and myosin proteins that allowed the muscle to contract and relax [20]. In this sense, the link between localized intramyo brillar glycogen content and muscle function, mediated by the Ca 2+ release from the sarcoplasmic reticulum (SR), has been established in the literature [21,22]. A study conducted on elite cross-country skiers showed a correlation between the reduction in skeletal muscle glycogen and release rate of Ca 2+ after completing 1 h of maximum e ort [22]. Moreover, signi cant di erences were found in glycogen content and Ca 2+ release after 4 h post-exercise between the group that consumed CHO (1 g/kg body weight/h) and the placebo one (water), suggesting that CHO intake during exercise might take on a major role in improving short term glycogen replenishment and muscle function [22]. Additionally, both short- and long-term recovery periods following exercise play an important role in ensuring a suitable return to physiological and metabolic homeostasis in

the group that consumed CHO (1 g/kg body weight/h) and the placebo one (water), suggesting that CHO intake during exercise might take on a major role in improving short term glycogen replenishment and muscle function [22]. Additionally, both short- and long-term recovery periods following exercise play an important role in ensuring a suitable return to physiological and metabolic homeostasis in athletes. When the neuromuscular function has been a ected, replenishment of glycogen stores is required to restore muscle function [23,24]. After exhaustive exercise and glycogen depletion, 36–48 h of high CHO diet (>7–9 g/kg body mass-BM) is needed to compensate muscle glycogen content [25]. However, when EIMD takes place, replenishment capacity is highly compromised, delaying this process by up to 10 days [26]. Moreover, the recovery kinetics of the neuromuscular function were studied following an ultra-marathon race, showing interesting results regarding peripheral and central fatigue [3].

Nutrients2020,12, 2094 3 of 17 While maximal voluntary activation and low frequency fatigue were recovered within 2 days, plasmatic Ca 2+ was still reduced at this point and muscle damage biomarkers returned to the baseline on day 5 [3]. In general, authors found that the majority of central and peripheral function indexes were recovered within 9 days [3], although it is generally accepted that central fatigue persists longer than peripheral fatigue [27]. Furthermore and with regard to glycogen replenishment and Ca 2+ release from the SR, Ortenblad et al. [22] found that after ingesting a high CHO diet within 22 h post-exercise, both glycogen content and the Ca 2+ release rate returned to baseline levels. Optimal nutritional protocols to ensure recovery following exercise have been extensively documented in the literature regarding glycogen resynthesis, protein synthesis and rehydration [25,28–30].Although few studies have been conducted with the ingestion of protein and carbohydrates during the exercise with the aim of improving recovery [31–33], ingested CHO quantities were lower than currently recommended [11]. To the best of the authors' knowledge, no research has been conducted using only CHO in high doses during exercise to optimize post-exercise recovery, which could prove very interesting when it comes to improving training capacity and performance in multi-stage competitions. As CHO intake represents a possible methodology not only to help improve performance during exercise, but also to improve recovery through di erent mechanisms such as limiting EIMD, decreasing internal exercise load and neuromuscular fatigue, maintaining suitable levels of blood glucose and sparing muscle and hepatic glycogen, the purpose of this research was to analyze the e ects of a high CHO (120 g/h) intake during a mountain marathon on 24 h recovery in elite runners in terms of neuromuscular function and high intensity run capacity in elite male ultra-endurance athletes. The main hypothesis of this research was to ascertain whether 120 g/h CHO intake could reduce neuromuscular fatigue by internal exercise load and improve long term recovery compared to current recommendations for ultra-endurance events (90 g/h) [34,35], and regular CHO intake on the part of athletes during such races

function and high intensity run capacity in elite male ultra-endurance athletes. The main hypothesis of this research was to ascertain whether 120 g/h CHO intake could reduce neuromuscular fatigue by internal exercise load and improve long term recovery compared to current recommendations for ultra-endurance events (90 g/h) [34,35], and regular CHO intake on the part of athletes during such races (60 g/h) [36]. 2. Materials and Methods 2.1. Participants and Experimental Protocol The current research was put together as a randomized trial with the aim of examining the e ects of 120 g/h of CHO intake during a trail marathon race on internal exercise load during exercise and muscle recovery 24 h following exercise. The 120 g/h of CHO supplementation was compared to international references for ultra-endurance events (90 g/h) [34,35], and regular CHO intake of athletes during such races (60 g/h) [36]. The use of 120 g/h was determined because previous studies have shown that after a training of gut tract it is possible to tolerate this amount [10,37] and because 120 g/h of CHO during an ultraendurance race has shown a lower internal exercise load and lower EIMD [15]. Thirty-one elite male athletes were assessed for eligibility in this study (including 2 trail skyrunner world champions from the International Trail Running Association (ITRA) and the International Association of Athletics Federations (IAAF)). After removing 5 athletes because they failed to meet the inclusion criteria (>5 years' experience in ultra-endurance training, having undertaken personalized training of the gut tract to enhance CHO absorption capacity and tolerance and not taken any drugs or performance supplements [38] to avoid any possible interference in the recovery process during the 1-week period prior to the race), 26 athletes were involved in the randomization process and went on to take part in the mountain marathon race. These 26 athletes were inspected by a medical doctor prior to the study in order to check they had no injury or disease. None of the runners were su ering from any disease, and none of them were taking any medication. The runners were randomized into three di erent

and went on to take part in the mountain marathon race. These 26 athletes were inspected by a medical doctor prior to the study in order to check they had no injury or disease. None of the runners were su ering from any disease, and none of them were taking any medication. The runners were randomized into three di erent groups by an independent statistician via a randomization sequence using SPSS software as follows: (I) group that was supplemented with 60 g/h of CHO (LOW;n=8; BMI: 23.0 2.9 kg/m 2 ), (II) group that was supplemented with 90 g/h of CHO (MED;n=9; BMI: 22.4 2.6 kg/m 2 ) and (III) group that was supplemented with 120 g/h of CHO (HIGH; n=9; BMI: 22.1 3.0 kg/m 2 ). The runners were instructed that as soon as they felt any damage and/or

Nutrients2020,12, 2094 4 of 17 gastrointestinal distress which might compromise their athletic performance, they should withdraw from the marathon to avoid interference in the results. As a result, 6 athletes withdrew during the race (3 with gastrointestinal discomfort– atulence and/or re ux and 3 with injury). The remaining athletes nished the marathon without experiencing any injuries and/or gastrointestinal di culties. Consequently, the sample included in the current research comprised 20 athletes, including 2 world champions (6 runners for the LOW, 7 runners for the MED and 7 runners for the HIGH) [15]. All participants ingested CHO during the race using the same gels made for this research at the University of Valladolid Physiology Laboratory (Soria) by an experienced pharmacist using a gel packaging machine. The gels contained 30 g of maltodextrin (glucose) and fructose (ratio 2:1) to increase exogenous CHO oxidation during exercise [39]. The athletes carried previously con gured GPS alarms to notify them that they should intake CHO gels every 15, 20 and 30 min during the mountain marathon race, with runners needing to consume 1/4, 1/3 or 1/2 of the total g of CHO per hour according to their group (HIGH, MED, LOW, respectively) (Figure). Although athletes drank waterad libitumduring the race, the participants ingested no food other than the gels. The athletes were instructed to extract the maximum content of the gels so that the residual amount was minimal. Likewise, all the athletes who nished the race con rmed through a questionnaire that all the gels had been taken at the time and in the manner previously indicated.Nutrients 2020, 12, x FOR PEER REVIEW 4 of 17 remaining athletes finished the marathon without experiencing any injuries and/or gastrointestinal difficulties. Consequently, the sample included in the current research comprised 20 athletes, including 2 world champions (6 runners for the LOW, 7 runners for the MED and 7 runners for the HIGH) [15]. All participants ingested CHO during the race using the same gels made for this research at the University of Valladolid Physiology Laboratory (Soria) by an experienced pharmacist using a gel packaging machine. The gels contained

research comprised 20 athletes, including 2 world champions (6 runners for the LOW, 7 runners for the MED and 7 runners for the HIGH) [15]. All participants ingested CHO during the race using the same gels made for this research at the University of Valladolid Physiology Laboratory (Soria) by an experienced pharmacist using a gel packaging machine. The gels contained 30 g of maltodextrin (glucose) and fructose (ratio 2:1) to increase exogenous CHO oxidation during exercise [39]. The athletes carried previously configured GPS alarms to notify them that they should intake CHO gels every 15, 20 and 30 min during the mountain marathon race, with runners needing to consume 1/4, 1/3 or 1/2 of the total g of CHO per hour according to their group (HIGH, MED, LOW, respectively) (Figure 1). Although athletes drank water ad libitum during the race, the participants ingested no food other than the gels. The athletes were instructed to extract the maximum content of the gels so that the residual amount was minimal. Likewise, all the athletes who finished the race confirmed through a questionnaire that all the gels had been taken at the time and in the manner previously indicated. Figure 1. Experimental design of study including pre- and post- tests and race fueling protocol and timing. CHO: Carbohydrate. The “marathon of Oiartzun” is a mountain marathon race (42.195 km) which began at 9:00 am in Oiartzun (Guipúzcoa-Spain) (10 °C, 60% humidity and 10 km/h wind speed) and was controlled by official chronometers. The race consisted of an entry and exit to a circuit that the runners had to complete 3 times. The height accumulated gradient of the mountain marathon race was 3980.80 m (1990.40 m positive and negative, respectively) (Figure 1), while the maximum and minimum height was 638.20 m and 3.80 m, respectively. During the race, the heat rate (HR) was documented using a HR monitor, and the mean HR (HRmean) and maximum HR (HRmax) during the event were also recorded. Prior to commencement of the study, all athletes received information about the purpose of it and associated risks and benefits. Subsequently,

maximum and minimum height was 638.20 m and 3.80 m, respectively. During the race, the heat rate (HR) was documented using a HR monitor, and the mean HR (HRmean) and maximum HR (HRmax) during the event were also recorded. Prior to commencement of the study, all athletes received information about the purpose of it and associated risks and benefits. Subsequently, everyone signed an informed consent. The study was designed according to the guidelines laid out in the Declaration of Helsinki and approved by the Human Ethics Committee at the Valladolid Health Area, Valladolid, Spain (PI 19-1345). 2.2. Dietary Assessment Figure 1. Experimental design of study including pre- and post- tests and race fueling protocol and timing. CHO: Carbohydrate. The “marathon of Oiartzun” is a mountain marathon race (42.195 km) which began at 9:00 am in Oiartzun (Guipózcoa-Spain) (10 C, 60% humidity and 10 km/h wind speed) and was controlled by o cial chronometers. The race consisted of an entry and exit to a circuit that the runners had to complete 3 times. The height accumulated gradient of the mountain marathon race was 3980.80 m (1990.40 m positive and negative, respectively) (Figure), while the maximum and minimum height was 638.20 m and 3.80 m, respectively. During the race, the heat rate (HR) was documented using a HR monitor, and the mean HR (HRmean) and maximum HR (HRmax) during the event were also recorded. Prior to commencement of the study, all athletes received information about the purpose of it and associated risks and bene ts. Subsequently, everyone signed an informed consent. The study was designed according to the guidelines laid out in the Declaration of Helsinki and approved by the Human Ethics Committee at the Valladolid Health Area, Valladolid, Spain (PI 19-1345).

Nutrients2020,12, 2094 5 of 17 2.2. Dietary Assessment By way of an inclusion criterion, it was stated that all athletes should have undertaken gut training which involved ensuring>90 g/h CHO intakes>2 days/week over the 4 weeks prior to the race [13,40]. Regarding diets and menus during the research period, all were put together individually for each athlete in accordance with international recommendations for ultra-endurance sports [34,35] by the same certi ed sport dietitian-nutritionist. The athletes obtained a personalized diet for a 48-h period prior to T1 and marathon race day with 9 g CHO/kg BM/day, 1.5 g protein/kg BM/day and 0.5 g fat/kg BM/day to adjust their glycogen content. This diet comprised, among other foods, vegetables, olive oil and sh, although it did not contain any fatty meat or butter [41]. Moreover, runners had breakfast (2 g CHO/kg BM) at the ElikaEsport Health Center 3 h prior to commencement of the mountain marathon race. This breakfast consisted of rice or paste, corn cereals with oat drink, cooked fruit and biscuits with jam, sweet quince or cheese. At the end of the marathon, each athlete ingested 1.2 g of CHO/kg BM with 0.3 g of whey isolate protein/kg BM in the recovery shakes. Within the next 24 h until T2, each runner consumed a suitable diet (9g CHO/kg BM, 1.5 g protein/kg BM and 0.5 g fat/kg BM) in order to replenish glycogen levels to almost 90–93% of previous muscle glycogen [25,42]. 2.3. Athletic Performance Test Runners attended the laboratory for an athletic performance test the week prior to the trail marathon race (T1) and 24 h after it (T2). The internal exercise load was estimated by training impulse (TRIMP) and athletic recovery was assessed using the Abalakov jump test (ABK), Drop jump test (DJ), Half Squat test (HST) and aerobic power-capacity test. The two test sessions were carried out at the ElikaEsport Health Center under standard conditions (temperature: 20 C and humidity: 55%) for both test sessions, and the tests were completed following a standardized 15-min warm-up. The warm-up involved 10 min of running with two 1-min speeding up (at

Study analyzes effects of carbohydrate intake on recovery in elite trail runners.